1. An agent comprising a polypeptide containing a sequence selected from the group consisting of the sequences SEQ ID NO.1-5, 7-9, 11-13, 15, 16 and 20-22, the sequence of fibrinopeptide A, the sequence of the plot of fibrinopeptide A, essentially homologous to mammalian species producing fibrinopeptide A, complement C3 sequences and the above sequences containing one or more conservative amino acid substitutions, wherein said agent is substantially free of detectable fibrinopeptide B.2. The agent according to claim 1, further comprising a therapeutically acceptable carrier. The agent according to claim 2, wherein the pharmaceutically acceptable carrier is selected from the group consisting of water, oil, edible oil, fatty acids, lipids, polysaccharides, cellulose, glycerol, glycol, and combinations thereof. The agent according to claim 3, characterized in that the edible oil is lemon oil, peppermint oil or grape seed oil. The agent according to claim 1, made in the form for oral, transmucosal, parenteral administration, administration to the lymphatic system or intravenous administration. The agent according to claim 1, characterized in that the biologically active form of the agent is released into the patient's system at a physiologically effective concentration. The agent according to claim 1, which is a food supplement. The agent according to claim 1, purified from the biological environment or obtained synthetically. A pharmaceutical composition comprising fibrinopeptide A or a fragment thereof and a pharmaceutically acceptable carrier, wherein fibrinopeptide A or a fragment thereof is present in a therapeutically effective amount, where therapeutically effective1. Агент, включающий полипептид, содержащий последовательность, выбранную из группы, состоящей из последовательностей SEQ ID NO.1-5, 7-9, 11-13, 15, 16 и 20-22, последовательности фибринопептида А, последовательности участка фибринопептида А, по существу гомологичного у видов млекопитающих, продуцирующ
